Here a little dtrace script which show the activiy while 5 minutes of IO per zones :

#!/usr/sbin/dtrace -s

#pragma D option quiet

io:::start
{
        @io[ zonename ] = sum(args[0]->b_bcount);
}

profile-5m
{
        exit(0);
}

END
{
        printf("zoneid\tIO in bytes\n");
        printa("%s\t%@d\n", @io);
}